Field of the Invention
The present invention relates to intelligent door lock systems, and more particularly to an intelligent door lock system with a torque limiter.
Description of the Related Art
Door lock assemblies often include deadbolts. Typically such an assembly included a latch which is depressed during closure of the door and, with substantially complete closure, extends into a recess of the door strike. Such a latch by itself is often easy to improperly depress-release by an unauthorized person, with a card-type element or even a pry bar. Also the outer knob assembly can be torqued off with a wrench to gain access to the mechanism and thereby to the room closed by the door. Deadbolts are not as susceptible to these unauthorized activities. Doors having deadbolts typically use a latch mechanism. This is because (1) the latch holds the door snug against rattling whereas the deadbolt by necessity must have clearance between it and the strike plate recess edges (but because of the clearance, the door can rattle), and (2) the latch automatically holds the door shut since it is only momentarily depressed during door closure from its normally extended condition and then extends into a door strike recess when the door is fully closed.
Except in rare devices where the deadbolt is operated by an electrical solenoid, the deadbolt, to be effective, must be manually thrown by a person inside the room or building, or if the deadbolt is actuatable by an external key, the person leaving the room or building must purposely engage the deadbolt by a key as the person leaves. However, if a person forgets to so actuate the deadbolt, either manually with an inner hand turn when inside, or by a key outside, an intruder need only inactivate the latch mechanism in order to gain unauthorized entry. Motel and hotel rooms often do not even have a key actuated deadbolt and thus are particularly susceptible to unauthorized entry and theft when the person is not in the room.
In recent years, mechanisms were developed to enable retraction, i.e. Inactivation, of the deadbolt simultaneously with the latch for quick release even under panic exit conditions. But to lock the door still required manual actuation of the deadbolt with the inner hand turn or a key on the outside.
In one door lock assembly a deadbolt is shift able between an extended lock position and a retracted position and means for shifting the deadbolt from the extended position to the retracted position which is characterized by biasing means for applying a bias on the deadbolt toward the extended lock position; restraining means for restraining the deadbolt in the retracted position against the bias of the biasing means and being actuatable to release the deadbolt to enable the biasing means to shift the deadbolt to the extended lock position; and trigger means. For actuating the restraining means to release the deadbolt and thereby allow the biasing means to shift the deadbolt to the extended lock position.
There are currently some electronic deadbolt lock arrangements. In one device, a lock has a bolt movable between locked and unlocked conditions. The lock has a manual control device that serves to operate the lock between locked and unlocked conditions. A power drive is coupled by a transmission to the manual control device. The lock is operated between the locked and unlocked conditions in response to operation of the power drive. A transmission mechanism couples the manual control device and the power drive, whereby the lock moves between the locked and unlocked conditions. The transmission mechanism is operable to decouple the power drive from the manual control means to enable the lock to be operated by the manual control device independently of the power drive.
Accordingly there is a need for an intelligent door lock system that limits torque.